Absolutely try? Well let's see...

Project Gotham Racing 4, I love it, arcade racer with a nice sim touch to it, the cities are rendered almost perfectly, I should know, my city is featured in that game

Gears Of War, it was a lot of fun to play the campaign in coop over system link, can't wait for the sequel to come out. Go ahead since you already got it, grab a friend if you can or play on live, it's a blast.

Lost Odyssey, if you like old school turned based rpgs, you should check it out. It's from the creators of final fantasy. While we're on the subject FF13 will be coming out to the 360, I'll check it out but I think I'll still stick with lost odyssey as my favorite rpg. Some people don't like it of course eh

Bioshock, nice retro feel in this one but please, don't play on easy, even my grandma could beat it on that difficulty.

Battlefield Bad Company, it's really fun to finally be able to blow up walls and pretty much everything that's standing. There's a good single player campaign mode too which can be quite funny at times. Riding on a golf course with a cart when ruskies are shooting at you, yay!

Some games which you probably know another one in the series like virtua fighter 5, beautiful katamari, dead or alive 4 (5 is coming out later this year I think), soulcalibur 4 (soon). On xbox live there's a sequel to portal and super street fighter 2 turbo hd which will be coming out, someday.

Finally, Ninja Gaiden 2. If you liked the first one, you should like that one too. Sure the camera isn't great in this one, but the action still is, plus decapitating ennemies is fun. Chop chop here goes a leg, still alive? Here goes an arm, another one, your head, die already! Just finished it on normal difficulty, damn that game is hard, a good challenge if you're looking for one.